The STEM is being used to characterize the reassociated hexagonal bilayer (HBL) structures obtained from bragments of the hemoglobins of Lumbricus, Tubifex, Arenicola, Amphiftite, Macrobdella, and the chlorocruins of Myxicola and Eudistylia. The results of stem on the reassociated hexagonal bilayer structures havebeen compared with the proposed "bracelet!' model of the quaternary structure of annelid hemoglobins and . chlorocruins and support the model. In this model subunits D 1 and D2 form a scaffolding or "bracelet" decorated with twelve complexes of subunits M and T. In this project the automatic ma s program was helpful in recognizin intact top view and side view molecules and measuring masses of thousands of particles. 'Similar measurements have been performed on a number of other hemoglobins. A protocol for isolation of earthworm hemoglobin from a live specimen with minimal purification has given molecules of extraordinary quality which we are considering as a new mass standard. Reassociation of the globin-chain-containing subunits with varying linker chains is being studied. It does not appear to require all of the linkers in order to assemble a HBL structure. Localization of the iron atoms is a potential STEM3 project.